U.S. patent number 10,644,193 [Application Number 16/116,820] was granted by the patent office on 2020-05-05 for method of manufacturing light-emitting element.
This patent grant is currently assigned to NICHIA CORPORATION. The grantee listed for this patent is NICHIA CORPORATION. Invention is credited to Yoshitaka Sumitomo, Haruki Takeda, Kazuki Yamaguchi.
United States Patent |
10,644,193 |
Yamaguchi , et al. |
May 5, 2020 |
Method of manufacturing light-emitting element
Abstract
A method of manufacturing a light-emitting element includes:
providing a wafer including: a substrate, and a semiconductor
structure; forming a plurality of modified regions inside the
substrate of the wafer by irradiating the substrate with a laser
beam; and separating the wafer into a plurality of light-emitting
elements after said irradiating the substrate with the laser beam.
Said forming the plurality of modified regions includes: scanning
the laser beam along a plurality of first lines, the plurality of
first lines extending in a first direction and being arranged in a
second direction, the first direction being parallel to the first
surface, the second direction intersecting the first direction and
being parallel to the first surface, and scanning the laser beam
along a plurality of second lines, the plurality of second lines
extending in the second direction and being arranged in the first
direction.
Inventors: |
Yamaguchi; Kazuki (Tokushima,
JP), Takeda; Haruki (Anan, JP), Sumitomo;
Yoshitaka (Tokushima, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
NICHIA CORPORATION |
Anan-shi, Tokushima |
N/A |
JP |
|
|
Assignee: |
NICHIA CORPORATION (Anan-Shi,
JP)
|
Family
ID: |
63407112 |
Appl.
No.: |
16/116,820 |
Filed: |
August 29, 2018 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20190067515 A1 |
Feb 28, 2019 |
|
Foreign Application Priority Data
|
|
|
|
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Aug 30, 2017 [JP] |
|
|
2017-165584 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
21/67092 (20130101); B23K 26/53 (20151001); H01L
21/67115 (20130101); H01L 33/007 (20130101); B23K
26/08 (20130101); H01L 33/0095 (20130101); B23K
26/364 (20151001); H01L 21/78 (20130101); B23K
26/0622 (20151001); B23K 2101/36 (20180801); B23K
2101/40 (20180801) |
Current International
Class: |
H01L
21/301 (20060101); B23K 26/40 (20140101); H01L
21/263 (20060101); B23K 26/08 (20140101); B23K
26/53 (20140101); B23K 26/0622 (20140101); H01L
21/78 (20060101); B23K 26/364 (20140101); H01L
21/67 (20060101); H01L 33/00 (20100101); H01L
21/268 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 402 984 |
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Jan 2012 |
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EP |
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2005-286218 |
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Oct 2005 |
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JP |
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2005-286218 |
|
Oct 2005 |
|
JP |
|
2008-078440 |
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Apr 2008 |
|
JP |
|
5119463 |
|
Jan 2013 |
|
JP |
|
2013-051260 |
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Mar 2013 |
|
JP |
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2014-147946 |
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Aug 2014 |
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JP |
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2015-122402 |
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Jul 2015 |
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JP |
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2015-130470 |
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Jul 2015 |
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JP |
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2017-084923 |
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May 2017 |
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JP |
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WO-2012/063348 |
|
May 2012 |
|
WO |
|
Primary Examiner: Turner; Brian
Attorney, Agent or Firm: Foley & Lardner LLP
Claims
What is claimed is:
1. A method of manufacturing a light-emitting element, the method
comprising: providing a wafer comprising: a substrate having a
first surface and a second surface, and a semiconductor structure
disposed on the second surface of the substrate; forming a
plurality of modified regions inside the substrate of the wafer by
irradiating the substrate with a laser beam; and separating the
wafer into a plurality of light-emitting elements after said
irradiating the substrate with the laser beam; wherein said forming
the plurality of modified regions includes: scanning the laser beam
along a plurality of first lines, the plurality of first lines
extending in a first direction and being arranged in a second
direction, the first direction being parallel to the first surface,
the second direction intersecting the first direction and being
parallel to the first surface, and scanning the laser beam along a
plurality of second lines, the plurality of second lines extending
in the second direction and being arranged in the first direction;
wherein a first interval, which is an interval between the
plurality of first lines in the second direction, is larger than a
second interval, which is an interval of the plurality of second
lines in the first direction, such that the plurality of first
lines and the plurality of second lines form a plurality of
elongated rectangular areas, each having long sides formed by the
plurality second lines and short sides formed by the plurality of
first lines; wherein, during irradiating the laser beam along one
of the plurality of first lines in said scanning the laser beam
along the plurality of first lines, the laser beam is irradiated at
a plurality of first positions that are arranged along the first
direction, and a first irradiation interval, which is an interval
between the plurality of first positions along the first direction,
is 2.0 .mu.m or less; wherein, during irradiating of the laser beam
along one of the plurality of second lines in said scanning the
laser beam along the plurality of second lines, the laser beam is
irradiated at a plurality of second positions along the second
direction, and a second irradiation interval, which is an interval
between the plurality of second positions along the second
direction, is in a range of 3.0 .mu.m to 3.5 .mu.m; wherein said
separating the wafer includes: separating the wafer into a
plurality of elongated bars along the plurality of second lines
forming the long sides of the plurality of elongated rectangular
areas, and after said separating the wafer into the plurality of
elongated bars, separating the elongated bars into the plurality of
light-emitting elements along the plurality of first lines forming
the short sides of the plurality of elongated rectangular
areas.
2. The method of manufacturing the light-emitting element according
to claim 1, wherein the second interval is 300 .mu.m or less.
3. The method of manufacturing the light-emitting element according
to claim 2, wherein an output of the laser beam in said scanning
the laser beam along the plurality of first lines and said scanning
the laser beam along the plurality of second lines is in a range of
100 mW to 150 mW.
4. The method of manufacturing the light-emitting element according
to claim 2, wherein said scanning the laser beam along the
plurality of second lines is performed after said scanning the
laser beam along a plurality of first lines.
5. The method of manufacturing the light-emitting element according
to claim 2, wherein the substrate is made of sapphire.
6. The method of manufacturing the light-emitting element according
to claim 2, wherein the first interval is 1 mm or more.
7. The method of manufacturing the light-emitting element according
to claim 1, wherein an output of the laser beam in said scanning
the laser beam along the plurality of first lines and said scanning
the laser beam along the plurality of second lines is in a range of
100 mW to 150 mW.
8. The method of manufacturing the light-emitting element according
to claim 7, wherein said scanning the laser beam along the
plurality of second lines is performed after said scanning the
laser beam along a plurality of first lines.
9. The method of manufacturing the light-emitting element according
to claim 7, wherein the substrate is made of sapphire.
10. The method of manufacturing the light-emitting element
according to claim 7, wherein the first interval is 1 mm or
more.
11. The method of manufacturing the light-emitting element
according to claim 1, wherein said scanning the laser beam along
the plurality of second lines is performed after said scanning the
laser beam along a plurality of first lines.
12. The method of manufacturing the light-emitting element
according to claim 1, wherein the substrate is made of
sapphire.
13. The method of manufacturing the light-emitting element
according to claim 1, wherein the first interval is 1 mm or more.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese Patent Application No.
2017-165584, filed on Aug. 30, 2017, the entire contents of which
are incorporated herein by reference.
BACKGROUND
Embodiments described herein relate to a method of manufacturing a
light-emitting element.
Forming element separation lines by performing laser irradiation in
a method of manufacturing a light-emitting element in which a
compound semiconductor to serve as a light-emitting layer is
stacked on a substrate is proposed.
SUMMARY
Increase in productivity in the method of manufacturing the
light-emitting element is desired. Certain embodiments of the
present invention provide a method of manufacturing a light
emitting device that allows for increasing productivity.
According to one embodiment, a method of manufacturing a
light-emitting element includes forming a plurality of modified
regions inside a substrate of a wafer by irradiating the substrate
with a laser beam, the wafer comprising: the substrate having a
first surface and a second surface, and a semiconductor structure
disposed on the second surface of the substrate; and separating the
wafer into a plurality of light-emitting elements after the step of
irradiating laser beam. The step of forming the plurality of
modified regions includes: scanning the laser beam along a
plurality of first lines, the plurality of first lines extending in
a first direction and being arranged in a second direction, the
first direction being parallel to the first surface, the second
direction intersecting the first direction and being parallel to
the first surface, and scanning the laser beam along a plurality of
second lines, the plurality of second lines extending in the second
direction and being arranged in the first direction. A first
interval, which is an interval between the plurality of first lines
in the second direction, is larger than a second interval, which is
an interval of the plurality of second lines in the first
direction. During irradiating the laser beam along one of the
plurality of first lines in the step of scanning the laser beam
along the plurality of first lines, the laser beam is irradiated at
a plurality of first positions that are arranged along the first
direction, and a first irradiation interval, which is an interval
between the plurality of first positions along the first direction,
is 2.0 .mu.m or less. The step of separating the wafer includes
separating the wafer into a plurality of bars along the plurality
of second lines. After separating the wafer into the plurality of
bars, separating the bars into the plurality of light-emitting
elements along the plurality of first lines.
A method of manufacturing a light emitting device according to one
embodiment of the present invention allows for increasing
productivity.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flowchart illustrating a method of manufacturing a
light-emitting element according to a first embodiment;
FIG. 2 is a schematic view illustrating a wafer used in the method
of manufacturing the light-emitting element according to the first
embodiment;
FIG. 3 is a schematic view illustrating a wafer used in the method
of manufacturing the light-emitting element according to the first
embodiment;
FIG. 4 is a schematic view illustrating a portion of the method of
manufacturing the light-emitting element according to the first
embodiment;
FIG. 5 is a schematic plan view illustrating a portion of the
method of manufacturing the light-emitting element according to the
first embodiment;
FIG. 6 is a schematic plan view illustrating a portion of the
method of manufacturing the light-emitting element according to the
first embodiment;
FIG. 7 is a schematic plan view illustrating a portion of the
method of manufacturing the light-emitting element according to the
first embodiment; and
FIG. 8 is a schematic plan view illustrating a portion of the
method of manufacturing the light-emitting element according to the
first embodiment.
FIG. 9 is a graph illustrating a result of an experiment related to
separation of light emitting elements.
DETAILED DESCRIPTION
Certain embodiments of the present invention will be described
hereinafter with reference to the accompanying drawings.
The drawings are schematic and illustrate technical ideas. In the
drawings, relationships between the thickness and width of each
portion, the proportions of sizes among corresponding portions,
etc., may not be the same as that in an actual light emitting
element. Further, the dimensions and proportions of the same
portion may be illustrated differently among drawings.
In the specification and drawings of the present application,
components similar to those in a drawing described earlier are
indicated by the same reference numerals, and their detailed
description may be omitted as appropriate.
FIG. 1 is a flowchart illustrating a method of manufacturing a
light-emitting element according to a first embodiment.
FIG. 2 and FIG. 3 are schematic views illustrating a wafer used in
the method of manufacturing the light-emitting element according to
the present embodiment. FIG. 2 is a cross-sectional view taken
along a line II-II of FIG. 3. FIG. 3 is a plan view as viewed along
arrow AR of FIG. 2.
As shown in FIG. 1, the method of manufacturing the light-emitting
element according to the present embodiment includes irradiating a
laser beam (step S110) and separating (step S120). The step of
irradiating a laser beam includes carrying out a first irradiation
(step S111) and carrying out a second irradiation (step S112). The
step of separating includes carrying out a first separation (step
S121) and carrying out a second separation (step S122).
A laser beam is irradiated on a wafer in the step of irradiating a
laser beam. An example of the wafer will be described below.
As shown in FIG. 2 and FIG. 3, the wafer 50W includes a substrate
50 and a semiconductor structure 51.
The substrate 50 has a first surface 50a and a second surface 50b.
The second surface 50b is the surface on the side opposite to the
first surface 50a. For example, the semiconductor structure 51 is
disposed on the second surface 50b.
The semiconductor structure 51 includes, for example, an n-type
semiconductor layer, an active layer, and a p-type semiconductor
layer. The n-type semiconductor layer is disposed between the
p-type semiconductor layer and the substrate 50. The active layer
is disposed between the p-type semiconductor layer and the n-type
semiconductor layer. The semiconductor structure 51 includes, for
example, a nitride semiconductor such as InxAlyGa1-x-yN
(0.ltoreq.x, 0.ltoreq.y, and x+y<1), etc. The peak wavelength of
light emitted by the active layer is, for example, in a range of
360 nm to 650 nm.
The direction from the second surface 50b toward the first surface
50a is referred to as a "Z-axis direction." A direction
perpendicular to the Z-axis direction is referred to as an "X-axis
direction." A direction perpendicular to the Z-axis direction and
the X-axis direction is referred to as a "Y-axis direction." The
first surface 50a and the second surface 50b extend along the X-Y
plane. The Z-axis direction corresponds to a thickness direction
(e.g., the depth direction) of the substrate 50.
As shown in FIG. 3, the semiconductor structure 51 includes, for
example, a plurality of regions 51r.
The plurality of regions 51r each correspond to one light-emitting
element. The plurality of regions 51r are arranged in a first
direction D1 and a second direction D2.
The first direction D1 is a direction parallel to the first surface
50a. The second direction D2 intersects the first direction D1 and
is parallel to the first surface 50a. The second direction D2 is
perpendicular to, for example, the first direction D1. In the
example, the first direction D1 is aligned with the Y-axis
direction. The second direction D2 is aligned with the X-axis
direction.
The substrate 50 is made of, for example, sapphire. The substrate
50 is, for example, a sapphire substrate (e.g., a c-plane sapphire
substrate). In the substrate 50, the first surface 50a may be
tilted with respect to the c-plane. In the case in which the
substrate 50 is a sapphire substrate, in one example, the first
direction D1 is aligned with the a-axis of the sapphire substrate.
In such a case, the second direction D2 is aligned with the m-axis
of the sapphire substrate.
The substrate 50 includes an orientation flat 55. In the example, a
direction in which the orientation flat 55 extends is aligned with
the second direction D2 of the wafer 50W. In the present
embodiment, any appropriate relationship is given between the first
direction D1 and a direction in which the orientation flat 55
extends. Further, any appropriate relationship is given between the
second direction D2 and the direction in which the orientation flat
55 extends.
A laser beam is irradiated on the wafer 50W having such a
structure. The wafer 50W is separated along the boundaries of the
plurality of regions 51r. A plurality of light-emitting elements is
obtained from the plurality of regions 51r.
FIG. 4 is a schematic view illustrating a portion of the method of
manufacturing the light-emitting element according to the present
embodiment.
FIG. 4 illustrates the irradiation of the laser beam. As shown in
FIG. 4, a laser beam 61 is irradiated on the substrate 50 of the
wafer 50W. In the example, the laser beam 61 enters the substrate
50 through the first surface 50a.
The laser beam 61 is emitted in a pulse form. For example, a Nd:YAG
laser, a titanium sapphire laser, a Nd:YVO4 laser, a Nd:YLF laser,
or the like is used as the laser light source.
A wavelength of the laser beam 61 is a wavelength of a light
passing through the substrate 50. Example of the laser beam 61
includes a laser beam having a peak wavelength in the range of 800
nm to 1200 nm.
The laser beam 61 is scanned along a direction parallel to the X-Y
plane. For example, the relative positional relationship between
the laser beam 61 and the substrate 50 is shifted along directions
parallel to the X-Y plane. The positional relationship along the
Z-axis direction (i.e., the positional relationship based on the
substrate 50) of the light condensing point of the laser beam 61
may be shifted.
For example, the laser beam 61 is irradiated separately along a
single direction aligned with the first surface 50a of the
substrate 50. The plurality of portions where the laser beam 61 is
irradiated are separated from each other along the single
direction. The plurality of portions where the laser beam 61 is
irradiated are aligned at an interval (i.e., a laser irradiation
interval Lp). The laser irradiation interval Lp corresponds to the
interval between the shots of the laser beam 61.
A plurality of modified regions 53 are formed inside the substrate
50 by the irradiation of the laser beam 61.
The laser beam 61 is concentrated at an inner portion of the
substrate 50. The energy of the laser beam 61 is concentrated at a
designated depth inside the substrate 50. Accordingly, the
plurality of modified regions 53 are formed. The interval of the
light condensing points of the laser beam 61 when forming the
plurality of modified regions 53 corresponds to the laser
irradiation interval Lp. The modified regions 53 are, for example,
regions embrittled due to the laser irradiation inside the
substrate 50.
For example, a crack propagates from the plurality of modified
regions 53. The crack extends in the Z-axis direction of the
substrate 50. Separation of the substrate 50 starts from the
crack.
For example, in a step of separating described below, a force
(e.g., a load, an impact, or the like) is applied, and the
substrate 50 is separated based on the crack.
Thus, in the step of irradiating a laser beam (step S110), the
laser beam 61 is irradiated on the substrate 50, and the plurality
of modified regions 53 are formed inside the substrate 50. For
example, the laser irradiation is performed along the first
direction D1 and the second direction D2.
Then, in the step of separating (step S120), the wafer 50W is
separated into a plurality of light-emitting elements after the
step of irradiating a laser beam. For example, the wafer 50W is
separated into the plurality of light-emitting elements by
performing separation along two directions.
An example of the step of irradiating the laser beam will be
described.
FIG. 5 is a schematic plan view illustrating a portion of the
method of manufacturing the light-emitting element according to the
present embodiment.
FIG. 5 illustrates the step of carrying out the first irradiation
(step S111). As shown in FIG. 5, the laser beam 61 is scanned along
a plurality of first lines L1 in step of carrying out the first
irradiation.
The plurality of first lines L1 extend in the first direction D1
and are arranged in the second direction D2. As described above,
the first direction D1 is parallel to the first surface 50a. The
second direction D2 intersects the first direction D1 and is
parallel to the first surface 50a. The plurality of first lines L1
are arranged at a first interval P1. The first interval P1 is a
distance along the second direction D2 between two first lines L1
adjacent to each other in the second direction D2.
For example, the plurality of first lines L1 are aligned with the
boundaries between the plurality of regions 51r arranged in the
second direction D2 (referring to FIG. 3).
As shown in FIG. 5, the laser beam 61 is irradiated at plurality of
first positions 61a in the irradiation of the laser beam 61 along
one of the plurality of first lines L1. The plurality of first
positions 61a are arranged along the first direction D1. The
interval of the plurality of first positions 61a corresponds to a
first irradiation interval Lp1. The first irradiation interval Lp1
is the distance along the first direction D1 between two first
positions 61a adjacent to each other in the first direction D1.
In the present embodiment, the first irradiation interval Lp1 is,
for example, 2.0 .mu.m or less. With such an interval, a breaking
strength in the step of separating process can be increased
sufficiently as described below in detail.
FIG. 6 is a schematic plan view illustrating a part of the method
of manufacturing the light-emitting element according to the
present embodiment.
FIG. 6 illustrates the step of carrying out second irradiation
(step S112). As shown in FIG. 6, the laser beam 61 is scanned along
plurality of second lines L2 in the step of carrying out second
irradiation.
The plurality of second lines L2 extend in the second direction D2.
The plurality of second lines L2 are arranged at a second interval
P2 in the first direction D1. The second interval P2 is the
distance along the first direction D1 between two second lines L2
adjacent to each other in the first direction D1.
For example, the plurality of second lines L2 are aligned with the
boundaries between the plurality of regions 51r arranged in the
first direction D1 (referring to FIG. 3).
The laser beam 61 is irradiated at a plurality of second positions
61b in the irradiation of the laser beam 61 along each of the
plurality of second lines L2 in the second irradiation process. The
plurality of second positions 61b are arranged along the second
direction D2. The interval of the plurality of second positions 61b
corresponds to a second irradiation interval Lp2. The second
irradiation interval Lp2 is the distance along the second direction
D2 between two second positions 61b adjacent to each other in the
second direction D2.
In one example, the first irradiation interval Lp1 is smaller than
the second irradiation interval Lp2. This allows for reducing
unintentional separation of the wafer in the step of separating, as
described below.
In the present embodiment, the first interval P1 (referring to FIG.
5) is larger than the second interval P2 (referring to FIG. 6).
An example of the step of separating will be described below.
FIG. 7 is a schematic plan view illustrating a part of the method
of manufacturing the light-emitting element according to the
present embodiment.
FIG. 7 illustrates the step of carrying out first separation. In
the first separation, the wafer 50W is separated into plurality of
bars 52 along the plurality of second lines L2. For example, the
wafer 50W is separated into the plurality of bars 52 by applying a
load to the wafer 50W along the second lines L2 using a blade. In
the present embodiment, in a single bar 52, the plurality of
regions 51r are arranged in the second direction D2.
FIG. 8 is a schematic plan view illustrating a part of the method
of manufacturing the light-emitting element according to the
present embodiment.
FIG. 8 illustrates the step of carrying out second separation. The
second separation is carried out after carrying out the first
separation. In the step of carrying out the second separation, the
bars 52 are separated into a plurality of light-emitting elements
51e along the plurality of first lines L1 after the step of
carrying out first separation. For example, the bars 52 are
separated into the plurality of light-emitting elements 51e by
applying a load to the bars 52 (i.e., the wafer 50W) along the
first direction D1 using a blade.
The first and second separation as described above is carried out
by cleaving, for example.
In the present embodiment as described above, the first interval P1
is larger than the second interval P2.
In each of the plurality of light-emitting elements 51e obtained by
the method of manufacturing as described above, the length along
the second direction D2 is longer than the length along the first
direction D1. Each of the plurality of light-emitting elements 51e
has a long side and a short side. A length of the long side
substantially corresponds to the first interval P1. A length of the
short side corresponds to the second interval P2.
In the present embodiment, the step of carrying out second
separation is performed after carrying out the first separation.
For example, a separation along singulation lines that extend along
the long sides (i.e., the second lines L2) is carried out, and then
the separation along the singulation lines that extend along the
short sides (i.e., the first lines L1) is carried out.
Alternatively, the separation along the second lines L2 can be
carried out after the separation along the first lines L1. In such
a case, carrying out the separation along the second lines L2 tends
to be difficult after the separation along the first lines L1. That
is, it is not easy to carry out the separation along the
singulation lines along the long sides of the plurality of
light-emitting elements 51e after the separation along the
singulation lines along the short sides of the plurality of
light-emitting elements 51e. This is because separation along the
long sides of the plurality of light-emitting elements 51e is finer
than separation along the short sides of the plurality of
light-emitting elements 51e, and thus the wafer that has been
separated along the short sides is not easily further separated
along the long sides compared to the case in which the wafer that
has been separated along the long sides is further separated along
the short sides.
In the present embodiment, the second separation is carried out
after carrying out the first separation. This allows for
facilitating separation of the substrate 50 into the plurality of
light-emitting elements.
Compared to the separation along the singulation lines that extend
along the short sides, unintentional separation occurs along the
short sides easily when separation is carried out along the
singulation lines that extend along the long sides. That is,
unintentional separation occurs more easily in the short sides than
in the long sides. According to the present embodiment,
unintentional separation in the short sides during separation along
the singulation lines that extend along the long sides can be
reduced.
Further, in the present embodiment, the first irradiation interval
Lp1 that is aligned with the first lines L1 is 2.0 .mu.m or less,
which is small. With such an interval, an unintentional separation
along the first lines L1 during the first separation can be
reduced.
As described below, reduction in the first irradiation interval Lp1
allows for increasing the breaking strength along the first lines
L1. Accordingly, for example, the separation along the first lines
L1 does not occur easily. For example, the occurrence of
unintentional separation due to an impact in the first separation
can be reduced further.
In the present embodiment, the laser beam 61 is irradiated at the
second irradiation interval Lp2 in the irradiation of the laser
beam 61 in the second irradiation. In the present embodiment, it is
favorable for the second irradiation interval Lp2 to be larger than
the first irradiation interval Lp1.
With a larger second irradiation interval Lp2, a breaking strength
along the second lines L2 in the irradiation of the laser beam 61
along the second lines L2 can be reduced. Accordingly, the
separation along the second lines L2 can be facilitated.
For example, in the separation along the second lines L2 (i.e., the
first separation), the separation along the second lines L2 can be
carried out even with a smaller load obtained by the blade or the
like. Because the separation along the second lines L2 can be
carried out by a smaller load, the load that is applied to the
first lines L1 can be also reduced; and the occurrence of the
unintentional separation along the first lines L1 can be reduced
further.
For example, the second irradiation interval Lp2 is, for example,
in a range of 3.0 .mu.m to 3.5 .mu.m. With such a second
irradiation interval Lp2, occurrence of the unintentional
separation can be reduced stably.
For example, unintentional separation occurs during two steps of
separation along two directions by, for example, application of an
uneven load to the substrate 50. Due to an unintentional
separation, defects such as chipping of the substrate occur. In the
present embodiment, as a condition of one of the first and second
laser irradiation, a condition with which a separation is less
easily achieved than with a condition of the other of the first and
second laser irradiation is employed. With such a condition, an
unintentional separation can be reduced.
In two separations along two directions, ease of separation along
one of the first and second direction may be different from ease of
separation along the other of the first and second direction. For
example, ease of separation may be different in accordance with the
crystal orientation of the substrate 50.
There is a reference example in which the difference between the
ease of separations are aimed to be reduced in such a case.
On the other hand, in the present embodiment, as the condition of
one of the first and second laser irradiation, a condition with
which a separation is less easily achieved than with a condition of
the other of the first and second laser irradiation can be
employed. In other words, the first irradiation interval Lp1 in the
first laser irradiation is set to be smaller than the second
irradiation interval Lp2 in the second laser irradiation process.
With the plurality of modified regions 53 formed in the first laser
irradiation process, the separation along the first lines L1 is not
easily carried out. Accordingly, portions to be separated in the
second separation can be prevented from being unintentionally
separated during first separation.
In the first embodiment, when the first separation and the second
separation are performed, the laser irradiation interval Lp is set
appropriately in accordance with the order of the separation (i.e.,
the cleaving). This allows for reducing an unintentional
separation.
According to the present embodiment, a method of manufacturing a
light-emitting element can be provided in which the productivity
can be increased.
Results of an experiment related to a breaking strength of the
wafer 50W after the laser irradiation will be described. A sample
used in the experiment includes the substrate 50 (the sapphire
substrate) and the semiconductor structure 51 in which nitride
semiconductors are stacked (referring to FIG. 2). A thickness of
the sample is approximately 120 .mu.m. The sample has a planar
shape of a rectangle, and a main surface of the sample has one side
(i.e., the long side) with a length of 2200 .mu.m and another side
(i.e., the short side) with a length of 2000 .mu.m. The laser beam
61 is irradiated on the sample along a center line parallel to the
long side of the sample. In the experiment, the laser irradiation
interval Lp is changed in a range of 1 .mu.m to 3.5 .mu.m for each
0.5 .mu.m. In the experiment, two types of conditions, i.e., the
case in which the laser beam 61 is irradiated along the m-axis of
the sapphire substrate and the case in which the laser beam 61 is
irradiated along the a-axis of the sapphire substrate, are
employed. The pulse period of the laser beam 61 is constant; and
the laser irradiation interval Lp is changed by changing the scan
rate of the laser beam 61. The laser beam 61 is emitted from a YAG
laser. The wavelength of the laser beam 61 is 1040 nm.
The breaking strength was measured for samples in which the laser
beam 61 was irradiated at the various laser irradiation intervals
Lp. A bending test was conducted for the measurement of the
breaking strength. A bending load was applied to the sample at
three points, and the load that caused breaking was determined as
the breaking strength.
FIG. 9 is a graph illustrating the result of the experiment
relating to the separation of the light-emitting elements.
The horizontal axis of FIG. 9 indicates the laser irradiation
interval Lp (in .mu.m). The vertical axis of FIG. 9 indicates a
breaking strength F1 (in newtons (N)). In FIG. 9, the values of the
breaking strength F1 when the laser beam 61 is irradiated along the
a-axis direction are indicated by round symbols. The values of the
breaking strength F1 when the laser beam 61 is irradiated along the
m-axis is indicated by triangular symbols. The average value of the
values of the breaking strength F1 when the laser beam 61 is
irradiated along the a-axis direction is indicated by square
symbols.
As shown in FIG. 9, the breaking strength F1 is increased when the
laser irradiation interval Lp is reduced. From the result in FIG.
9, when the laser irradiation interval Lp is 3 .mu.m, substantially
similar tendencies are observed for the laser irradiation along the
m-axis direction and the laser irradiation along the a-axis.
It can be seen from FIG. 9 that the breaking strength F1 started to
increase when the laser irradiation interval Lp is 2.5 .mu.m or
less. The breaking strength F1 was greatly increased when the laser
irradiation interval Lp is 2.0 .mu.m or less. On the other hand,
the breaking strength F1 was stably reduced when the laser
irradiation interval Lp was in a range of 3.0 .mu.m to 3.5
.mu.m.
In view of the description above, it is preferable for the first
irradiation interval Lp1 to be 2.0 .mu.m or less. It is preferable
for the second irradiation interval Lp2 to be 3.0 .mu.m or more
(3.5 .mu.m or less). With such intervals, there is a large
difference between the fracture strength F1 of the first laser
irradiation and the fracture strength F1 of the second laser
irradiation.
It can be seen from FIG. 9 that the minimum value of the breaking
strength F1 when the laser irradiation interval Lp is 1.5 .mu.m or
less is greater than the maximum value when the laser irradiation
interval Lp is 3.0 .mu.m or more.
Therefore, it is more preferable for the first irradiation interval
Lp1 to be 1.5 .mu.m or less. Thereby, even when variations are
taken into consideration, a sufficient difference is obtained for
the fracture strength F1.
Thus, in the present embodiment, the laser irradiation interval Lp
is selected appropriately in accordance with the order of
separations (i.e., cleavings). This allows for reducing
unintentional separation.
The inventors had previously assumed that reduction in intervals of
the laser irradiation would facilitate breakage of a substrate.
However, as described above, it was found that reduction in
intervals of the laser irradiation increases the breaking strength
F1, which allows the substrate to be not easily separated. It is
considered that the separation does not occur easily because the
plurality of modified regions are formed densely at the inner
portion of the substrate along the scanning line of the laser beam,
and overlapping of the plurality of modified regions with each
other allows for reducing separation of the substrate.
In the present embodiment, it is preferable for the second interval
P2 to be 300 .mu.m or more. For example, with the second interval
P2 of less than 300 .mu.m, an unintentional separation tends to
easily occur along the first lines L1 during the first separation.
In the present embodiment, with the first irradiation interval Lp1
of a predetermined value, the unintentional separation can be
reduced even in the case in which the second interval P2 is 300
.mu.m or less.
In the present embodiment, it is preferable for the first interval
P1 to be 1 mm or more, and more preferably to be in a range of 1 mm
to 3 mm.
In the present embodiment, it is preferable for the output of the
laser beam 61 in the step of carrying out the first irradiation and
the step of carrying out the second irradiation to be in a range of
100 mW to 150 mW. With the output higher than 150 mW, for example,
damage may occur in the semiconductor structure 51 (e.g., in the
light-emitting elements 51e). With the output lower than 100 mW,
for example, the modified regions 53 are not formed easily, or the
crack does not extend easily from the modified regions 53.
Therefore, the separation of the substrate 50 may be difficult.
With the output in a range 100 mW to 150 mW, for example,
separation can be facilitated while reducing damage of the
semiconductor structure 51.
In the present embodiment, it is preferable for the second
irradiation to be carried out after the first irradiation.
As described above, the first interval P1 of the plurality of first
lines L1 in the first irradiation is larger than the second
interval P2 of the plurality of second lines L2 in the second
irradiation. For example, the number of the plurality of first
lines L1 per unit surface area is smaller than the number of the
plurality of second lines L2 per unit surface area.
As described above, the plurality of modified regions 53 are formed
by the irradiation of the laser beam 61; the crack that occurs from
the plurality of modified regions 53 propagates; and the substrate
50 is separated. With a greater number of times of scanning of the
laser beam 61, the number of the modified regions 53 also increased
easily, and the stress (e.g., the compressing stress) at the inside
of the substrate 50 is increased. In the state in which the
compressive stress at the inside of the substrate 50 is increased,
even if the modified regions 53 are formed, the crack that occurs
from the modified regions 53 does not extend easily. Therefore, the
substrate 50 is not easily separated. Reduction in compressive
stress of the interior of the substrate 50 allows for facilitating
separation of the substrate 50.
By carrying out the first irradiation, in which the number of scans
is smaller, earlier, the second irradiation can be carried out in a
state in which the compressive stress inside the substrate is
relatively small. For example, in the case in which the first
irradiation, in which the number of scans is smaller, is carried
out after the second irradiation, in which the number of scans is
larger, the first irradiation is carried out in a state in which a
strong compressing stress acts. In such a case, even if the
modified regions 53 are formed in the step of carrying out the
first irradiation, the crack does not extend easily; therefore, it
is not easy to perform the cleavage of the substrate. In the
present embodiment, difficulty in extension of the crack from the
modified regions obtained by the first irradiation and the second
irradiation can be reduced. Accordingly, the substrate 50 is
separated easily.
EXAMPLE
In one example, the wafer 50W in which the semiconductor structure
51 that includes a nitride semiconductor was disposed on a sapphire
substrate is provided. A thickness of the sapphire substrate is 120
.mu.m. The wavelength of the laser beam 61 is approximately 1060
nm. The output of the laser beam 61 is approximately in a range of
100 mW to 150 mW.
In the step of irradiating laser beam, the first direction D1 is
parallel to the a-axis of the sapphire substrate. The second
direction D2 is parallel to the m-axis of the sapphire substrate.
The first interval P1 is 1100 .mu.m. The second interval P2 is 200
.mu.m. In a first condition, the first irradiation interval Lp1 is
1.5 .mu.m; and the second irradiation interval Lp2 is 3.0
.mu.m.
In the step of performing separation, the first separation was
carried out along the second lines L2; subsequently, the second
separation process was carried out along the first lines L1.
Among obtained light emitting elements, light emitting elements in
which chipping or the like occurs due to unintentional breaking was
determined to be poor quality. In the example, the ratio of light
emitting elements of poor quality was 0.5%.
Reference Example
In a reference example, the first irradiation interval Lp1 is 3.0
.mu.m. The other conditions of the reference example are the same
as those of the example described above. In the reference example,
the ratio of light emitting elements of poor quality was 2.0%.
According to the manufacturing method of the example, the ratio of
light emitting elements of poor quality can be reduced, and
productivity can be increased.
According to certain embodiments, a method of manufacturing a
light-emitting element can be provided in which the productivity
can be increased.
In the specification of the application, "perpendicular" and
"parallel" refer to not only strictly perpendicular and strictly
parallel but also include, for example, a slight deviation from
strictly perpendicular and strictly parallel due to manufacturing
processes, etc. That is, the terms "perpendicular" and "parallel"
encompass substantially perpendicular and substantially parallel
configurations, respectively.
Exemplary embodiments of the invention are described above with
reference to specific examples. However, the scope of the invention
is not limited to those specific examples. For example, specific
configurations of wafers, substrates, semiconductor structures,
light-emitting elements, lasers, etc., that are used in
manufacturing of a light emitting element may be appropriately
selected from known art by a person skilled in the art, and
variations of such specific configurations are included in the
scope of the present invention as long as a person skilled in the
art can similarly implement the invention and similar effects can
be obtained.
Further, combination of any two or more components of the specific
examples within the extent of being technically possible can be
included in the scope of the invention as long as the combination
does not depart from the spirit of the invention.
Moreover, all methods of manufacturing light-emitting elements that
are appropriately modified by a person skilled in the art from the
methods of manufacturing light-emitting elements described above as
certain embodiments of the invention also are within the scope of
the invention as long as the modified method does not depart from
the spirit of the invention.
Various other variations and modifications can be made by those
skilled in the art within the spirit of the invention, and it is
understood that such variations and modifications are also
encompassed within the scope of the invention.
* * * * *